Screen stencil and method of making same



f 1944- J. B. BRENNAN ET AL I 2,338,091

SCREEN STENCiL AND METHOD OF MAKING SAME Filed April 18, 1939 JOSEPH .aBEEN/VAN & LEONA' MAEsH P'atented Jan. 4, 1944 SCREEN s'rsncn. ANDmz'rnon or MAKIN SAME Joseph B. Brennan and Leona Marsh, Euclid,

Ohio: said Marsh assignor to said Brennan Application Apru 1a, 1939.Serial No. 263,570 I 18 Claims. ('01. 101-1283) This invention relatesto screen stencils and methods of making same and the presentapplication is a continuation in part of our copending applicationsSerial No. 115,208 and No. 175,240

filed December 10, 1936, and November 18, 1937,

respectively.

As describedv in our copending applications aforesaid screen stencilshaving very important advantages over those heretofore'known can beproduced by blocking the interstices of a screen such as a fine wovenwire mesh with a metal chemically different from the material formingthe screen. applying a resist to the plate so formed, for example by aphotographic method, and then etching away the blocking metal in thoseportions of the plate which are not covered by the resist. The etchingoperation is carried, out preferably by a re-agent which will attack anddissolve the blocking metal but will not substantially attack thematerial of the screen. Screen stencils so producer. are accurate anddurable and may be advantageously used for many purposes as, forexample; for applying designs in enamel to metal or for applying designsto glass for various printing and dyeing operations as well as for signsand dials. v

' In our prior applications the preferred forms of screen. stencilscomprised metallic screens filled with or attached to a metal chemicallydifferent from the material forming the screen.

" In screen stencils made according to this application we "preferablyemploy three different metals of different chemical characteristicsineluding a perforate member such as a woven wire screen'formed of oneinorganic material such; as a metal, a metallic sheet of a differentmetal which is secured to theperforated member by a metallic bond formedof still another metal. By this combination of elements and, by theproper selection Of materials it is'poss'ible to provide screen stencilsby which a design canbe reproj, 'duced with great accuracy and fidelityevendown if to very minute details. Further,.it is possible to providescreen stencils of varying thickness so that deposits of varying amountsof material can be'made in the subsequent screening operations.

By the methods described herein screen stencils made according to ourinvention can be effectively and economically produced.-

The essential characteristics the claims.

In the drawing Figure 1 is a plan view of a preferred form of screenstencil plate made according to our inventionand having a design etchedare summarized in therein; Figure 2-is 'a sectional view of the plateindicated in Figure 1 taken along the line 22 of Figure 1 on a greatlyenlarged scale; Figures 3,. 4, and 5 are diagrammatic illustrationsshowing steps of preferred methods of producing our 1 screen stencils.

As shown in Figures .1 and 2 a screen stencil made according to ourinvention preferably comprises a perforate member such as a Woven wirescreen l0 having a thin metal plate It secured to one side thereof, theplate being bonded to the screen by another metal l2 which at leastpartially fills the interstices of the screen. The materials comprisingthe screen, the filling in metal l2 and the sheet II are preferablychosen so that they can be subjected to selective etching action wherebythe material of the sheet ll may be etched away until the underlyingmaterial I2 is exposed and thereafter the bonding material 12 may bedissolved bya reagent which will attack neither the sheet I 1 nor thewires making up the screen l0. As an example of a procedure which wehave found to be very satisfactory a stainless steel screen! of about150 meshwoven of wires about 0.002 in diameter may be sandwiched betweena piece of tinfoil I 2 of about 0.004" thickness and Further novelfeatures and advantages of our invention will become apparentfromthefollow- 5 ing description of preferred forms therjof, referme being madeto the accompanyin a piece of copperv foil ll' of about .002" thicknessas indicated diagrammatically in Figure 3. The three pieces may then bepressed tightly between steel plates or rolls, one-or both of which-maybe heated sufficiently to cause the tin to melt. If

desired, the tin can be pressed into the screen by a fluid underpressure, or by a resilient or yieldable material such as rubber, andthereafter subjected to heat. The result of this process'is that theinterstices of the stainless steel screen are filled as shown in Fig. 2,with tin, which also functions to secure the copper foil to thestainless steel screen.

In utilizing such a plate in' the manufacture of a screen stencil aresist may be applied to the flat surface of the copper in a mannerknown to those killed in'the art for example by the usualphotographicmethods. Then the plate may be etched by an etching solution orsolutions which will attack the copper and tinwithout substantiallyaffecting the stainless steel wires; A solution of ferric chloride inwater is suitable.

By this method the possibility of side etching oil the copper toll iseliminated and thus fine details may be accurately preserved. The resultor the etching is indicated diagrammatically in Figure 2, wherein itwill be seen that the copper and the tin have been removed in regionIll, leaving only the stainless steel wires. The copper toll is etchedwith sharp edges as at It, thus accurately preserving the detail or thedesign. even though the tin may be subjected to some side etching asshown at I! in Figure 2.

It will be noted thatthe screen is preferably spaced slightly above theflat surface ofthe copper foil as' shown in the drawing. When suchscreen is used for example in applying an enamel design the flat surfaceI8 01' the copper sheet is placed in contact with the article to whichthe design is to be applied and powdered enamel or frit is rubbedthrough the screen onto the surface which is to receive the designthrough the apertures such as the opening it. The sharp,

clearly defined edges I 6 of the etched areas in-- sure the productionof accurate designs with all details properly reproduced. Also byvarying the thickness of the copper foil, the distance between the.screen and the flat surface ll can be varied which will result in acorresponding variation in the amount of material or pigment depositedon the surfaces beingdecorated during the screening operation; that is,if the distance between the surface ll! of the copper foil and thescreen is increased, a greater thickness of enamel or frit can bedeposited while, if the distance is reduced, a thinner layer will bedeposited. In carrying out .enameling'operations we are able, byemploying foils of sufficient thickness, to deposit enamel in suchquantities that the design will appear definitely in relief after it hasbeen fired, and yet by reason of the sharpness of the edges of theetched-away portions and the smoothness and flatness of the surface it,there is practically no loss of definition.

Various other methods of securing the screen to the plate may beemployed. Foa example, as shown diagrammatically in Figure 4 a screenIla this means the sprayed tin will cause the copper sheet to adhere tothe screen. Ifdesired, the sprayed assembly may be subjected to heat orpressure or both to compact the spray deposited metal and to bond thethree metals more firmly together.

' Various modifications and changes may be made in the methods andarticles describedherein. For example, the screen'may be-partially orcompletely filled in by dipping the screen in mol- .ten tin and thenremoving the excess or by electro-plating the screen with'tin.Thereafter the coated screen maybe assembled with a sheet of copper andsubjected toheat, and pressure if desired, to form a unitary assembly.In every case, suitable flux may be employed to cause the materials toadhere properly. Various other materials may be substituted for thosedescribed herein. Thus the copper sheet or foil may be replaced by aniron sheet or foil in which case the iron may be etched by a solution ofcopper sulfate and hydrochloric acid, and thereafter the tin may beremoved ride. (FeClz).

Zinc foil or nickel foil may also be employed, with the selection ofproper etchants. Other metals, such as low melting point alloys, may besubstituted for the tin described herein. The screen may be made ofvarious materials such as Monel metal or bronze. The screen may becomposed of any suitable perforate material such as a thin perforatedmetallic sheet or, if desired, parallel closely spaced wires may be usedin place of woven wires. Variations may also be made in the methods ofbonding. These and other modifications of our invention will be readilyunderstood by those skilled in the art. Therefore it is to be understoodthat our invention is not limited to the preferred forms thereofdisclosed herein, or in any manner other than by the appended claimswhen given the range of equivalents to forming the screen and'having animperforate may be employed in conjunction with a sheet of copper foilHa tinned as indicated at lZa. The

screen is placed against the tinned surface of the copper foil andpressed into the tin preferably by a roll or plate heated to asuilicient temperahire to cause the tin to melt or to become plastic.

The amount of pressure required will, of course,

be increased if the degree of heating is reduced.

The tin may also be cold pressed in or'hammered in as by a drop hammer.By varying the thickness of the tinand by subjecting the screen cally inFigure 5. According to this method a stainless steel screen lflb may besuperposed upon a copper plate I lb and then the assembly sprayed withfinely divided molten particles of tin for example by a Schoop pistolindicated at l9. By

metallic sheet bonded to said screen by said fill ing-inmetal, andsubjecting certain areas of the plate to the action of a reagent adaptedto dis-. solve said metallic sheet and said filling-in metal withoutsubstantially attacking the material of the screen, thereby dissolvingthe metallic sheet and the fllling-in'metal without dissolving thescreen in-such areas.

2. A method oi'making screen stencils which includes the steps offorming a screen stencil plate comprising a screen ofcorrosion-resisting material having the openings therethrough at leastpartially closed by a layer of tin adhering thereto, and having animperforate copper sheet bonded to said screen by said tin, andsubjecting certain areas of said plate to the action of a re-' agentadapted to dissolve said copper sheet and said tin without substantiallyattacking the screen, thereby dissolving the copper and the tin withoutdissolving the screen in such areas.

3. A method of making screen stencils which includes the steps offorming a screen stencil plate comprising a stainless steel screenhaving the openings therethrough closed by a layer of tin adheringthereto, and having an imperiorate iron sheet bonded to said screen bysaid tin, and subby a solution of iron chloa,sse,oe1

thereto, and thereafter.,,etching,away the metal.

Iecting certain., .areas ofvsaid plate-to theaction l of a reagentadapted to dissolve said iron sheet and said tin without substantiallyattacking the stainless steel screen, thereby dissolving the copper andthe tin without dissolving the screen in such areas. Y

4. A method of making screen stencils which includes. the steps offorming a screen stencil plate comprising a screen having the openingstherethrough closed by a filling-in metal chemically different from thematerial forming the screen and having an imperforate metallic sheetbonded to said screen by said filling-in metal, applying a resist to aportion of the area of said plate, subjecting the, plate to the actionof a reagent adapted to dissolve said metallic sheet until said metallicsheet is dissolved away in the areas of said plate which are notprotected by said resist, and thereafter subjecting the plate to theaction of a reagent adapted to dissolve said filling-in metal withoutsubstantially attacking said metallic sheet, the material of the screen,or the resist.

5. The method according to claim 4, wherein the screen is composed ofstainless steel, the filling-in metal consists of tin. and the metallicsheet consists of copper.

6. A method of making screen stencils which includes the steps offorming a screen stencil plate comprising a stainless steel screenhaving the openings therethrough closed by a layer of tin and having animperforate copper sheet bonded to said screen by said tin, applying aresist to a portion of the area of said plate; subjecting the plate tothe action of a solution of ferric chloride until said copper sheet isdissolved away in the areas of said plate which are not protected bysaid resist, and thereafter subjecting the plate to the action of asolution of cupric chloride to dissolve said tin without substantiallyattacking said copper sheet, the screen or the resist.

7. The method of making screen stencils which includes the steps ofbonding a metallic sheet to a metallic screen composed of a metaldiflerent trom the metal of the sheet by means of a. bonding metaldifferent from both the metal of the sheet and the metal of the screen,applying a resist to a portion cit the exposed surface of the sheet, andetching away the sheet and the bonding metal in the areas not protectedby the resist without substantially etching the screen.

8. The method according to claim 7 wherein a copper sheet is bonded to astainless steel screen by tin.

9. The method of making a screen stencil which includes the steps ofplacing a sheet of metal having a relatively high meltins p int incontact with one side of a metallic screen composed of a differentmetal, placing a sheet of metal having a relatively low melting pointadjacent theother side of said screen, fusing the low melting pointmetal without fusing the metal of the screen or the'high melting pointmetal, to thereby fill the interstices of the screen and to bond therelatively high melting .point metal of the sheet and the bonding metalin certain areas without substantially etching the screen in such areas.a

10. The method of'making a screen stencil which includes the steps ofassembling a sheet of metal having a relatively high melting point witha metallic screen composed of a different metal and a sheet of a metalhaving a relatively low melting point, and fusing the low melting pointmetal without fusing the metal of the screen orthe high melting pointmetal to thereby 1111 the interstices of the screen and bond therelatively high melting point metal thereto.

11. The method according to claim 10 wherein the high melting pointmetal consists of copper and the low melting point metal consists oftin.

12. The method of making screen stencils which includes the steps ofdisposing a metallic screen upon a sheet of another metal, sprayingfinely divided molten metal thereon to bond the screen and sheettogether, and thereafter etching away the metal of the sheet and thebonding nietal in certain areas without substantially etching the screenin such areas.

13. The method of making screen stencils which includes the steps ofdisposing a stainless steel screen upon a sheet of copper, sprayingfinely divided tin thereon to bond the screen and sheet together, andthereafter etching away the tin and the copper in certain areas withoutsubstantially etching the screen in such areas.

14. The method of making screen stencils which includes the steps ofbonding a layer of metal to a sheet composed of a metal having a highermelting point than the metal of the layer, heating the layer to softenit and embedding a metallic screen therein, the metallic screen beingcomposed of a metal different from the metal oi the layer and the metalof the sheet. and themafter etching. away the sheet and metallic layerin certain areas without substantially etching the screen in such areas.I

15. In themanufacture of screen stencils of the tin and embedding astainless steel metallic 7 screen therein.

17. A screen stencil blank or plate adapted to have a design etchedtherein comprising a stainless steel screen bonded to a sheet of coppermetal .by a bond composed of tin.

18. A screen stencil blank or plate adapted to have a design etche'dtherein comprising a layer of tinembedded in a fine meshed metal gauzeattached to a thin layer'of copper.

I JOSEPH B. BRENNAN.

LEONA MARSH.

